Fuel injection nozzle

ABSTRACT

In a fuel injection nozzle of the inwardly opening type wherein the spring-loaded nozzle valve is opened by metered pulses of high pressure fuel delivered in timed sequence by a fuel injection pump, an improved nozzle valve which reduces engine gaseous emissions and exhaust smoke by permitting a reduced sac volume. The minimum fuel flow through the valve is controlled by the valve element configuration rather than the valve seat intersection with the sac as in the conventional nozzle. The present nozzle construction facilitates manufacturing and permits a change of the valve delivery characteristics by modification of the valve element rather than the less accessible valve seat. The present construction provides an increased valve seat flow capacity for a given seat angle and valve lift.

United States Patent [1 1 Butterfield et al.

[ 51 Sept. 17, 1974 FUEL INJECTION NOZZLE [73] Assignee: Ambac Industries, Inc., Springfield,

Mass.

[22] Filed: Sept. 10, 1973 [21] Appl. No.: 395,828

[52] US. Cl. 239/96, 239/533 [51] Int. Cl. F02m 41/16, B05b 1/30 [58] Field of Search 239/96, 101, 533, 553, 239/562, 570, 584, 585, 590

[56] References Cited UNITED STATES PATENTS 3,391,871 7/1968 Fleischer et al. 239/533 FOREIGN PATENTS OR APPLICATIONS 906,603 9/1962 Great Britain 239/533 504,341 12/1954 Italy 239/533 651,704 l/1963 ltaly 239/533 Primary ExaminerRobert S. Ward, Jr. Attorney, Agent, or Firm-l-lowson and Howson [5 7 ABSTRACT In a fuel injection nozzle of the inwardly opening type wherein the spring-loaded nozzle valve is opened by metered pulses of high pressure fuel delivered in timed sequence by a fuel injection pump, an improved nozzle valve which reduces engine gaseous emissions and exhaust smoke by permitting a reduced sac volume. The minimum fuel flow through the valve is controlled by the valve element configuration rather than the valve seat intersection with the sac as in the conventional nozzle. The present nozzle construction facilitates manufacturing and permits a change of the valve delivery characteristics by modification of the valve element rather than the less accessible valve seat. The present construction provides an increased valve seat flow capacity for a given seat angle and valve lift.

10 Claims, 7 Drawing Figures PATENIED 3. 836.080

FIG].

FIGE. (PRIOR ART) FUEL INJECTION NOZZLE The present invention relates generally to fuel injection nozzles for delivery of atomized fuel into the cylinders of internal combustion engines of the diesel type. More particularly, the invention relates to an improved fuel injection nozzle of the closed inwardly opening type having a nozzle valve design which minimizes engine gaseous emissions and exhaust smoke, facilitates manufacturing of the nozzle, and increases the valve seat flow capacity.

In the closed type of fuel injection nozzle, the nozzle tip extends into the engine combustion chamber so that the nozzle spray orifices are in a position to direct a spray of atomized fuel in a predetermined pattern within the combustion chamber. The spray orifices in a typical nozzle fan outwardly from a chamber known as the nozzle sac located immediately below the nozzle valve. A problem with the conventional nozzle is the boiling of the residual fuel in the sac chamber during combustion of the injected fuel in the engine chamber. Vaporized fuel from the sac escapes through the spray orifices into the combustion chamber but arrives too late for combustion with the injected charge and instead is exhausted from the engine with the products of combustion thereby increasing gaseous emissions and visual smoke. Although only a small amount of fuel escapes unburned in this manner, it is highly visible, particularly in the exhaust of automotive engines such as highway trucks. With the increasing emphasis on emission controls for automotive engines, the present invention is a timely and important advance in reducing the emission levels of diesel engines.

A further related problem is the chemical breakdown of the residual fuel in the sac chamber under the intense heat conditions of the combustion chamber, resulting in a fouling of the spray orifices and a buildup of carbon on the nozzle tip.

In the present invention the sac volume is substantially reduced in comparison to conventional nozzles, thereby reducing the amount of fuel remaining in the sac cavity following injection and minimizing the unburned fuel escaping to the exhaust from this source. It is the novel shape of the valve element which permits the reduction in sac volume. The valve element configuration is such as to establish the control point of minimum fuel flow with the valve element rather than at the intersection of the valve seat and sac as in the conventional nozzle. The sac may be smaller since it may now have converging walls. Allowance is unnecessary for finish grinding of the valve seat, and the valve element need not project into the sac when the valve is open. Since the seat flow characteristic of the nozzle may be controlled by machining the valve element rather than the relatively inaccessible sac and seat intersection, this operation is greatly facilitated. The improved shape of the valve element further increases the flexibility of manufacture of the nozzle since it permits an increase of the fuel flow area with a given valve lift simply by modifying the valve element with only a slight resultant increase in the volume of the sac cavity. Furthermore, since the improved valve shape provides increased flow at the seat for any given valve lift and any specific seat angle, it is therefore possible to reduce the valve lift in many applications to obtain the lowest possible nozzle seat and spring stresses for increased service life.

It is accordingly a first object of the present invention to provide an improved fuel injection nozzle which reduces engine gaseous emissions and visual smoke, and nozzle fouling by minimizing the volume of the nozzle sac cavity.

A further object of the invention is to provide an improved fuel injection nozzle as described having a novel valve element configuration which facilitates manufacturing of the nozzle.

Another object of the invention is to provide a fuel injection nozzle as described wherein the fuel flow characteristics of the nozzle may be varied by a change in the valve element configuration with only a slight resultant increase in the volume of the sac cavity.

Another object of the invention is to provide a fuel injection nozzle as described having a novel valve element configuration which provides either l increased fuel flow without changing valve seat angle or valve lift or (2) reduction in nozzle seat and spring stresses by reducing valve lift and maintaining existing fuel flow.

Additional objects and advantages of the invention will be readily apparent from the following detailed description of an embodiment thereof when taken together with the accompanying drawings wherein:

FIG. I is a partial side view partly in section of a nozzle assembly embodying the present invention;

FIG. 2 is an enlarged sectional view of the lower end of a conventional fuel injection nozzle;

FIG. 3 is an enlarged view of the lower end of the nozzle shown in FIG. 1, showing the nozzle valve in the closed position;

FIG. 4 is a view similar to FIG. 3 with the valve shown in the open position;

FIG. 5 is a partial sectional view taken along line 55 of FIG. 4;

FIG. 6 is a sectional view taken along line 6-6 of FIG. 4; and

FIG. 7 is a sectional view taken along line 77 of FIG. 4.

Referring to the drawings, FIG. 1 illustrates the lower portion of a fuel injection nozzle assembly generally designated 10 which for installation in an engine is secured to a nozzle holder (not shown) by the partially illustrated cap nut 12. The nozzle assembly 10 includes a nozzle body 14 having a lower cylindrical portion 16 and an upper concentric cylindrical portion 18 of larger diameter. The cap nut 12 bears against the shoulder 20 formed at the juncture of the body portions 16 and 18.

A valve element 22 is disposed within a concentric bore 24 in the nozzle body 14. The valve element includes a cylindrical upper portion 22a and a tapered lower portion 22b, and terminates at its lower end in a valve tip 28 having a novel configuration as described in detail below. The valve tip is adapted to cooperatively engage a frusto-conical valve seat 30 in the nozzle body which extends coaxially downwardly from the bore 24. A smaller chamber 32 known in the art as a sac is disposed immediately beneath and in communication with the valve seat. A plurality of spray orifices 34 extend outwardly through the valve body substantially perpendicularly to the walls of the sac. The exterior of the nozzle body in the region of the sac is shaped in a nipple-like configuration to permit a substantially lateral direction of the fuel spray even in the case of asymmetrical spray orifices.

The valve element is downwardly spring-loaded into the closed position illustrated in FIG. 1. Fuel from a fuel injection pump flows downwardly through annular passage 36 between the valve element and the bore wall and acts against the valve element to open the valve when the fuel pressure exceeds the spring force. The high pressure fuel flows into the sac, and is atomized as it passes out through the spray orifices into the combustion chamber. A drop in fuel pressure permits the valve to close under the spring force, cutting off the injection.

As indicated above, the present invention comprises essentially the cooperative configurations of the valve element tip, the valve seat and the sac, which details are most readily apparent from the views of FIGS. 37. Prior to considering the details of the invention in these areas, however, it would be advantageous to review conventional nozzle tip construction as shown in FIG. 2 where elements common to the above described nozzle are designated by the same numerals with a prime subscript.

Referring to FIG. 2, the prior art nozzle assembly includes a nozzle body 14 and a valve element 22 disposed within the bore 24 of the body. The 'body 14' includes a valve seat 30' having a frusto-conical configuration, the diametrically opposed walls of which when viewed in section as in FIG. 2 form the included angle B. The valve tip 28 comprises a conical surface which intersects the tapered valve element portion 22b to form the circular edge 40. The diametrically opposed edges of the conical valve tip 28 form therebetween the included angle V which is a slightly larger angle than angle B of the valve seat so that the valve element will engage the valve seat in its closed position along the circular edge 40. The sac 32 of the conventional nozzle is relatively large and of cylindrical shape with a semispherical end for reasons set forth below. The spray orifices 34 extending outwardly from the sac 32' direct atomized fuel in a predetermined spray pattern into the engine cylinder when the nozzle valve is opened.

In the prior art nozzle described, the minimum fuel flow area when the valve is in the open position occurs at the circular control edge 42 formed by the intersection of the valve seat and the cylindrical walls of the sac. Since the typical nozzle is many times smaller than the views shown (the spray orifices are barely visible to the unaided human eye), the machining of the valve seat and sac, which are relatively inaccessible at the bottom of the valve body is a difficult and time consuming operation. Since the valve seat 30' in the conventional nozzle is finish ground after heat treatment, it can be understood that the sac walls must be cylindrical and concentric so that the control edge 42 will not change as the valve seat is ground. Furthermore, a sufficient volume of the sac must be provided to permit the extending valve tip conical surface 28' to protrude into the sac cavity. This protruding portion cooperates with the edge 42 when the valve elements is in the open position to control the rate of fuel flow. The conventional nozzle accordingly must include a sac of an undesirably large volume.

Referring back to the present nozzle construction as shown in the enlarged views of FIGS. 3-7, the valve tip 28 comprises a frusto-conical surface 44, diametrically opposed faces of which are angled at the included angle V as shown in FIG. 3. This frusto-conical surface 44 intersects the tapered valve element surface 22b at the circular edge 46. The valve tip terminates in a conical surface 48, diametrically opposed faces of which form the included angle A as shown in FIG. 3. The conical surface 48 intersects the frusto-conical surface 44 to form the circular control edge 50 which has the diameter D as illustrated in FIG. 3. The diametrically opposed walls of the valve seat 30 as shown in FIG. 3 form the included angle B which is slightly less than the included angle V of the valve element surface 44. Accordingly, the valve element will contact the seat along the edge46 in the closed position as shown in FIG. 3. The sidewalls of the sac 32 have a frusto-conical configuration, diametrically opposed faces of which form the included angle C therebetween. The angle C being a smaller angle than the angle B of the valve seat, a circular edge 52 is formed at the intersection of the sac with the valve seat.

From the sectional views of FIGS. 5-7, it can be seen that the area of minimum fuel flow in the open position of the valve is located between the control edge 50 (FIG. 6) of the valve element and the valve seat. The angle A of the conical surface 48 is chosen so as to insure an increased flow area below the control edge 50 for any position of the valve element.

The operation of the present nozzle is best shown in FIG. 4 wherein the valve element is illustrated in the open position. As shown by the flow indicating arrows,

the high pressure fuel passes from the annular passage 36 between the valve seat and the valve element sur' faces 44 and 48 into the sac 32. The rate of flow is determined by the minimum fuel flow area adjacent the control edge 50, the diameter D of which governs the nozzle delivery characteristics. From the sac 32, the fuel passes through the spray orifices 34 and exits as an atomized spray 54 into the engine combustion chamher.

With the control of nozzle seat minimum fuel flow at the valve element control edge 50, the injection characteristics of the nozzle can be effected by machining the surface 48 while maintaining the angle A. This serves to enlarge the diameter D of the control edge 50, thereby increasing the fuel flow area with only a slight resultant increase in the sac volume.

Since the minimum fuel control point is shifted from its conventional location at the intersection of the sac and seat walls, the sac can be shaped with frustoconical walls to minimize its volume. The sac wall angle C should, however, be less than the seat angle B to provide run-out clearance for seat grinding. The sac depth can be considerably reduced since no cylindrical sac is required for seat flow control. Furthermore, the valve element tip with the present construction does not extend to an appreciable depth into the sac. For these several reasons, the present nozzle valve construction permits a substantial decrease in sac volume in comparison to conventional nozzles, with a consequent reduction in engine gaseous emission and visual smoke. It has been found in at least one instance that a nozzle utilizing the present design need have only 1 1 percent of the sac volume that would be necessary using the conventional construction. The reduction in sac volume coupled with the greatly facilitated manufacture and increased seat flow capacity of the nozzle possible with the present construction accordingly provides both an improved nozzle performance from an emission control standpoint and increased economies and flexibility of manufacture.

While a primary advantage of the present nozzle construction is the permissible reduction of the sac volume, it would of course be possible to utilize the valve construction with a conventional sac configuration and still achieve many of the described functional advantages such as increased flow capacity, ease of manufacture and extended service life.

Manifestly, changes in details of construction can be effected by those skilled in the art without departing from the spirit and scope of the present invention.

We claim:

1. In a fuel injection nozzle assembly comprising a nozzle body, a bore within said body, a valve element disposed within said bore for recipricatory movement between open and closed positions, a frusto-conical valve seat at the lower end of said bore, the lower end of said valve element being adapted to engage said valve seat to seal the passage therebetween, a sac beneath said valve seat in communication therewith, spray orifices extending outwardly through said valve body from said sac, and means for introducing pressurized fuel into said bore above said valve seat, the improvement comprising a circular control edge on said valve element lower end which defines in cooperation with said valve seat the minimum fuel flow area between said valve element and said valve seat in the open position of said valve element.

2. The invention claimed in claim 1 wherein said control edge is formed by the intersection of two surfaces of revolution on said valve element.

3. The invention claimed in claim 2 wherein one of said surfaces of revolution is a conical surface.

4. The invention claimed in claim 1 wherein the side walls of said sac have a frusto-conical configuration.

5. The invention claimed in claim 4 wherein the included angle of said frusto-conical valve seat is greater than that of said sac walls.

6. In a fuel injection nozzle assembly comprising a nozzle body, a bore within said body, a valve element disposed within said bore for recipricatory movement between open and closed positions, a frusto-conical valve seat at the lower end of said bore, the lower end of said valve element being adapted to engage said valve seat to seal the passage therebetween, a sac beneath said valve seat in communication therewith, spray orifices extending outwardly through said valve body from said sac, and means for introducing pressurized fuel into said bore above said valve seat, the improvement wherein said valve element lower end configuration comprises a conical surface at the valve element tip, and a frusto-conical surface adjacent said conical surface, the intersection of said conical and frusto-conical valve element surfaces forming a circular control edge which cooperates with said valve seat to define the minimum fuel flow area between said valve element and said valve seat in the open position of said valve element.

7. The invention claimed in claim 6 wherein the included angle of said valve element frusto-conical surface is greater than that of said valve seat.

8. The invention claimed in claim 6 wherein the included angle of said valve element conical surface is greater than that of said valve element frusto-conical surface so that the fuel flow area below said control edge is greater than that at said control edge at any position of said valve element.

9. The invention claimed in claim 6 wherein the side walls of said sac have a frusto-conical configuration.

10. The invention claimed in claim 9 wherein the included angle of said frusto-conical valve seat is greater than that of said sac walls. 

1. In a fuel injection nozzle assembly comprising a nozzle body, a bore within said body, a valve element disposed within said bore for recipricatory movement between open and closed positions, a frusto-conical valve seaT at the lower end of said bore, the lower end of said valve element being adapted to engage said valve seat to seal the passage therebetween, a sac beneath said valve seat in communication therewith, spray orifices extending outwardly through said valve body from said sac, and means for introducing pressurized fuel into said bore above said valve seat, the improvement comprising a circular control edge on said valve element lower end which defines in cooperation with said valve seat the minimum fuel flow area between said valve element and said valve seat in the open position of said valve element.
 2. The invention claimed in claim 1 wherein said control edge is formed by the intersection of two surfaces of revolution on said valve element.
 3. The invention claimed in claim 2 wherein one of said surfaces of revolution is a conical surface.
 4. The invention claimed in claim 1 wherein the side walls of said sac have a frusto-conical configuration.
 5. The invention claimed in claim 4 wherein the included angle of said frusto-conical valve seat is greater than that of said sac walls.
 6. In a fuel injection nozzle assembly comprising a nozzle body, a bore within said body, a valve element disposed within said bore for recipricatory movement between open and closed positions, a frusto-conical valve seat at the lower end of said bore, the lower end of said valve element being adapted to engage said valve seat to seal the passage therebetween, a sac beneath said valve seat in communication therewith, spray orifices extending outwardly through said valve body from said sac, and means for introducing pressurized fuel into said bore above said valve seat, the improvement wherein said valve element lower end configuration comprises a conical surface at the valve element tip, and a frusto-conical surface adjacent said conical surface, the intersection of said conical and frusto-conical valve element surfaces forming a circular control edge which cooperates with said valve seat to define the minimum fuel flow area between said valve element and said valve seat in the open position of said valve element.
 7. The invention claimed in claim 6 wherein the included angle of said valve element frusto-conical surface is greater than that of said valve seat.
 8. The invention claimed in claim 6 wherein the included angle of said valve element conical surface is greater than that of said valve element frusto-conical surface so that the fuel flow area below said control edge is greater than that at said control edge at any position of said valve element.
 9. The invention claimed in claim 6 wherein the side walls of said sac have a frusto-conical configuration.
 10. The invention claimed in claim 9 wherein the included angle of said frusto-conical valve seat is greater than that of said sac walls. 